To the Editor.—I call your attention to the incorrect use of percentages in the editorial "Estrogen Therapy and Endometrial Carcinoma," which appeared in the Archives (138:526-527, 1978). The studies mentioned in the editorial showed a four- to 14-fold risk (or a 400% to 1,400% risk), not a 4% to 14% greater risk. Similarly, for cigarette smoking and lung cancer, there is a nine- to 20-fold risk, not a 9% to 20% greater risk as quoted. I hope that your readers do not take literally this trivialization of the large relative risks involved.